The present invention relates to an improvement of a gas burner.
In general the conventional gas burners such as gas-fired water heaters are provided with pilot burner-safety means which can automatically shut off the supply of a gas fuel to the gas burner when the pilot flame cone is blown off for any reason. However, this safety device cannot respond to reduction of the oxygen content in the air, below a normal level, so that incomplete combustion results, generating a large amount of carbon monoxide (CO) which represents a very serious hazard to the lives and health of people who is not aware of the incomplete combustion.
In order to overcome the above problem, there has been proposed and demonstrated a pilot burner which is so designed and constructed that when the content of the oxygen in the air supplied to the gas burner drops below a normal level, the flame cone may lift off the mouth of the pilot burner. The lift-off of the pilot flame cone in turn is detected by a suitable sensor so that the deficiency of the oxygen content in the air supplied to the gas burner may be detected and in response to the output signal a suitable safety means such as a control valve is closed so as to interrupt the supply of gas fuel. The pilot burner of the type described is effective when LNG or LPG is burned because of its slow burning velocity, but is ineffective when a town or city gas is burned because it has a high burning velocity. That is, as will as described in detail below with reference to FIGS. 1-5, the response is so slow that before the change in height of the pilot flame cone is detected, the main burner has generated a large amount of CO. When a city or town gas is burned, the height of the pilot flame cone is relatively high under normal conditions; that is, when sufficient oxygen is supplied, but when the content of oxygen in the air drops below a normal level, the height of the pilot flame cone is reduced so slowly that the difference between the normal and abnormal heights of the pilot flame cone cannot be detected immediately.